全文获取类型
收费全文 | 4018篇 |
免费 | 894篇 |
国内免费 | 1625篇 |
专业分类
化学 | 3032篇 |
晶体学 | 261篇 |
力学 | 344篇 |
综合类 | 192篇 |
数学 | 574篇 |
物理学 | 2134篇 |
出版年
2024年 | 14篇 |
2023年 | 49篇 |
2022年 | 125篇 |
2021年 | 139篇 |
2020年 | 120篇 |
2019年 | 103篇 |
2018年 | 109篇 |
2017年 | 162篇 |
2016年 | 117篇 |
2015年 | 208篇 |
2014年 | 237篇 |
2013年 | 355篇 |
2012年 | 310篇 |
2011年 | 389篇 |
2010年 | 400篇 |
2009年 | 364篇 |
2008年 | 408篇 |
2007年 | 428篇 |
2006年 | 344篇 |
2005年 | 326篇 |
2004年 | 263篇 |
2003年 | 200篇 |
2002年 | 210篇 |
2001年 | 190篇 |
2000年 | 251篇 |
1999年 | 142篇 |
1998年 | 72篇 |
1997年 | 61篇 |
1996年 | 55篇 |
1995年 | 35篇 |
1994年 | 48篇 |
1993年 | 56篇 |
1992年 | 42篇 |
1991年 | 27篇 |
1990年 | 25篇 |
1989年 | 21篇 |
1988年 | 19篇 |
1987年 | 22篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1971年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有6537条查询结果,搜索用时 171 毫秒
131.
De Jiang LI He Qing FU 《中国化学快报》2006,17(5):625-627
1, 3, 4-Oxadiazoline derivatives are found to possess significant biological activities such as antifungal1, insecticidal2, CNS depressant3-5, anticonvulsant effects and plant growth accelerator. They are highly important heterocycles, and have been used … 相似文献
132.
乙烯在纳米催化剂InVO4-TiO2上的可见光降解 总被引:1,自引:0,他引:1
The InVO4-TiO2 nano-crystalline photocatalyst was prepared by sol-gel method and characterized by DRS, FTIR, Raman and XRD. The photocatalytic activities of the prepared sample were investigated by photocatalytic degradation of ethylene in the gaseous phase under visible light irradiation (λ>450 nm). The results indicate that both of pure TiO2 and InVO4 or their simple mixture show no photocatalytic activities for degradation of ethylene under visible light irradiation. However, as-synthesized InVO4-TiO2 catalyzes the degradation of ethylene into CO2 under visible light irradiation. In addition, the interaction between InVO4 and TiO2 results in some structural distortion to all the crystal forms of TiO2 in as-synthesized catalyst InVO4-TiO2. 相似文献
133.
Self-assembly of Ag(Ⅰ) nitrate, 1,3-bis(4-pyridyl)propane (bpp) and phthalic acid monopotassium salt (KHphth) in CH3OH-H2O solution produced the title complex,{[Ag(bpp)]2(Hphth)(NO3)·(H2O)2}n, which was characterized by single-crystal X-ray diffraction,elemental analysis, IR spectrum, and photoluminescent spectrum. Single-crystal X-ray analysis revealed that the complex crystallizes in a monoclinic system, space group P21/c, with α =15.4174(5), b = 8.6398(2), c = 25.2466(8) (A), β = 91.072(1)°, V = 3362.34(17) (A)3, Z = 4,C34H37N5O9Ag2, Mr = 875.43, Dc = 1.729 g/cm3, μ = 1.228 mm-1, F(000) = 1768, the final R =0.0749 and wR = 0.1580 for 5754 reflections with I > 2σ(I). The Ag atom is coordinated by two N atoms from two bpp molecules in an approximately linear geometry. The Ag(Ⅰ) ions are linked by the bpp molecules to form one-dimensional zigzag chains propagating along the c axis. The Hphth-and nitrate counter-ions are bridged by solvent water molecules through hydrogen bonds to generate a one-dimensional chain extending along the b axis. Electrostatic interactions between cations and anions, extensive hydrogen bonds and π-π interactions are responsible for the three-dimensional supramolecular structure. In the solid state, the compound exhibits blue photoluminescence with the maximum at 436 nm upon excitation at 344 nm. 相似文献
134.
栝楼蛋白 2: 栝楼蛋白部分化学结构的初步测定 总被引:5,自引:0,他引:5
栝楼蛋白(Trichobitacin)是从栝楼(Trichosanthes kirilowiiMaxim, Cucurbitaceae)中新发现的核糖体失活蛋白, 分子量为27,228; pI为9.6。应用基质辅助的激光解析飞行时间质谱(MALDI-TOF-MS)和快原子轰击质谱法(FAB-MS)分别测定胰蛋白酶酶解栝楼蛋白和天花粉蛋白(Trichosanthin)的混合肽质谱, 通过比较发现了一些分子量相同的肽。由于这两种蛋白质都来源于栝楼块根, 同源性比较强, 所以这些肽序列在两种蛋白质中基本一样; 再结合蛋白N-端自动顺序仪测定栝楼蛋白N-端的结果, 确定了栝楼蛋白N-端38个氨基酸的顺序, 栝楼蛋白经胰蛋白酶酶解后所得肽段用HPLC分离纯化, 再用蛋白质自动顺序仪, DABITC/PITC双偶合手工法和质谱法共确定了栝楼蛋白N-端, C-端等100多个氨基酸残基的序列。 相似文献
135.
ZHENG Li-Min FU Yan LIN Jian-Jun XIN Xin-QuanCoordination Chemistry State Key Laboratory Department of Chemistry Nanjing University Nanjing Jiangsu China 《中国化学》1994,12(3):243-247
The solid-solid state reactions of o-aminobenzoic acid with Zn(OAc)2.2H2O, Cu(OAc)2 .H2O, Ni(OAc)2.4H2O and Mn(OAc)2.4H2O result in the formation of corresponding complexes M(OAB)2 (M = Zn(Ⅱ), Cu(Ⅱ), Ni(Ⅱ), Mn(IⅡ)). XRD, IR and elemental analysis methods have been used to characterize the solid products. The activation energies of these reactions, which are calculated from the kinetic data obtained by means of the isothermal electrical conductivity measurement method, have been found to increase in the order: Cu(OAc)2.H2O(37.7 kJ.mol-1)~Mn(OAc)2.4H2O (39.7kJ.mol-1) < Zn(OAc)2.2H2O (56.3 kJ.mol-1) < Ni(OAc)2.4H2O (85.2 kJ.mol-1). The trend is related to their crystal structures. 相似文献
136.
Effects of simultaneously doped and deposited Ag on the photocatalytic activity and surface states of TiO2 总被引:8,自引:0,他引:8
Ag-TiO2 catalysts with different Ag contents were prepared via a sol-gel method in the absence of light. Based on the characterizations of XRD, photoluminescence (PL), surface photovoltage spectroscopy (SPS), field-induced surface photovoltage spectroscopy (FISPS), and XPS as well as the evaluation of the photocatalytic activity for degrading rhodamine B(RhB) solutions, it was found that the Ag dopant promoted the phase transformation as well as had an inhibition effect on the growth of anatase crystallite. The PL and SPS intensities were decreased with increasing Ag content, indicating that the Ag dopant could effectively inhibit the recombination of the photoinduced electrons and holes. However, the active sites capturing the photoinduced electrons reduced, while the Ag content exceeded 5 mol %. At rather low Ag dopant concentrations, the migration and diffusion of Ag+ ions were predominant, while at rather high Ag dopant concentrations, the migration, diffusion, and reduction of Ag ions simultaneously occurred. The Ag-TiO2 photocatalysts with appropriate content of Ag (Ag species concentration is from about 3 to 5 mol %) possessed abundant electron traps so as to be favorable for the separation of the photoinduced electron-hole pairs, which could greatly enhance the activity of the photocatalysts. From the results of FISPS measurements, it could be found that the impurity bands and abundant surface states were introduced into the interfacial layer of TiO2 because of Ag simultaneously doping and depositing, which could improve the absorption capability for visible light of the photocatalysts. 相似文献
137.
138.
A scheme for remotely preparingan arbitrary five-qubit Brown state by using three three-qubit GHZ states as the quantum channel is proposed. It is shown that, after the sender performs two different three-qubit projective measurements, the receiver should introduce two auxiliary qubits and employ suitable C-NOT gates, Toffoli gate and unitary operations on his qubits, the original state can be recovered with unit probability. Compared with the previous scheme, the advantage of the present scheme is that the entanglement resource can be reduced. 相似文献
139.
140.